vincent



Jan. 8, 1929.

J. G. VINCENT INTERNAL COMBUSTION ENGINE Filed Dec. 18, 1926 2 Sheets-Sheet v JESSE E. Vizvasu' atio: "Q11 Jan. 8, 1929. 1,698,078

J. G. VINCENT INTERNAL COMBUSTI 0N UNGI NE Filed Dec. 18, 1926 2 Sheets-Sheet 2 V L ll] 1.1 R? Q K W Q JESSE Z5. VINCENT.

Patented Jan. 8, v1929.

UNITED STATES PATENT OFFICE.

JESSE G. VINCENT, OF DETROIT, MICHIGAN, ASSIGNOR TO PACKARD MOTOR CAR COMPANY, OF DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN.

INTERNAL-COMBUSTION ENGINE.

Application filed December 18, 1926.

This invention relates to internal combustion engines and particularly to the cylinder, piston and related parts.

In the manufacture of internal combustion engines, particularly those used for automobiles, motor boats, etc., the clearance between the piston and the cylinder must be rather close in order to make the engine operate quietly and yet it must not be so close as to cause the piston to seize or stick when it becomes hot. This clearance is a matter of a few thousandths of an inch and a thousandth one way or another may determine whether the piston can be used or must be rejected. It is of considerable advantage, therefore, if an extra thousandth of clearance can be provided without sacrificing any other requirements because this would greatly facilitate manufacture and more certainly insure that every engine coming off the line would have pistons loose enough to not seize or stick when operated at high speed an appreciable length of time.

But it has been found that if this additional one or two thousandths clearance is provided the pistons are loose in the cylinders and anoise results which is technically referred to as piston slap. This slap is a sudden movement of the piston from one side of the cylinder to the other and usually occurs at the top of the stroke and more particularly at the beginning of the firing stroke on four stroke cycle engines. It may occur, however, at the bottom of either stroke under some conditions. The slap is a disagreeable clicking noise and engineers have spent much time and money in trying to find a positive cure for it without at the same time making it necessary to hold the manufacturing department of the factory to impracticable limits of manufacture.

It has been proposed, as shown in the patent to E. F. Roberts, No. 1,138,892, dated May 11, 1915, that piston slap may be obviated by slightly offsetting the piston pin in the piston. This produces an unbalanced effect so far as the piston head area is concerned and it seems in most cases to have entirely eliminated piston slap where the looseness of the piston is not too great. It probably does not and is not expected to eliminate piston slap in the case of very loose pistons.

In the use of Roberts pistons'usually made of cast iron, it was found that in some cases Serial No. 155,566.

piston slap occurred at the beginning of the intake stroke or at the bottom of either stroke, probably due to the unbalance of the weight of the piston caused by the offset, these slaps occurring when unbalance of head pressure was of less consequence as when the engine was operating at high speed with light throttle opening. A remedy for this form of piston slap was proposed in the patent to J. G. Vincent, No. 1,545,930, dated July 14:, 1925, the piston being so formed that it was substantially balanced as to weight on opposite sides of its pin bearing while at the same time its unbalance as to head area was maintained.

As the necessity for increased speeds in automobile engines became apparent which speeds had to be obtained, if possible, with out adding vibration, aluminum pistons became almost a necessity because of their lesser inertia. But with the greater coefficient of expansion of aluminum over cast iron it was usual to provide greater clearance between the piston and cylinder when cold, and with the centered piston pin, piston slap became even more pronounced. Offsetting the pin according to the Roberts patent proved of some assistance, but even here, at the beginning of the firing stroke, piston slap still prevailed to some extent with the same amount of offset as had been used in practice with cast iron pistons. On the latter pistons, for instance, a 3 g inch offset was ordinarily used on a 3 or 3 inch piston. Of course the offset might be increased and perhaps better results obtained but experience showed that this further offset would bring in other obj ections that might be as bad as the slap. For instance, there would be greater wear on the pistons due to the greater angle of the connecting rod, and the unbalance of the weight would be increased to the point where it might be necessary to cast a lug on the narrow side of the piston to balance it as to weight, and this would destroy to some extent the advantage gained by making the pistons of aluminum. \Vith about the same offset as used on cast iron pistons, it was found that the unbalanced weight of the aluminum piston became inconsequential, but if the ofiset was increased materially it would be objectionably noisy at high speeds.

The problem which confronted the engineers, therefore, was that of quieting these aluminum pistons without at the same time bringing other disadvantages into effect.

And one of the objects of this invention is to provide means to prevent the sudden slapping across from one side of the cylinder to with such ofi set piston pin.

Another object of the invention-is to so unbalance the head pressures on a light weight piston, and so mount the piston, that piston slap will be eliminated even though relatively large clearance is provided between the piston and the cylinder.

. Referring to the drawings, the principal parts of the engine illustrated in Fig. 1 are indicated as follows: 10 is the crank case in the mainbearings of which is mounted a crank shaft 11, and a sprocket 12 thereon operates a chain 13 for driving a generator shaft 14 and cam shaft 15; mounted upon the crank case is a cylinder block 16 in which operate the pistons 17 there is a connecting rod 18 having its lower end connected to a crank on the shaft 11 and its upper end pivoted in the piston 1?; at one side of the cylinder are the intake and exhaust ports and the valves therefor, one of the valves, the exhaust valve, being indicated at 19; these valves are operated from the cam shaft by the usual mechanism; detachably mounted upon the cylinder block 16 is a head 20 which is formed with a recess 21 extending over a portion of the cylinder and over the valve ports, thus forming a combustion chamber, and a spark plug 22 is suitably arranged in the head to fire the charge in the chamber. A

portion of the cylinder head is brought down close to the top of the cylinder as indicated at 23 and is preferably made flat and arranged to cover substantially that half of the cylinder farthest removed from the valves and it is so positioned that there is only slight clearthe piston and cylinder and towards the valve side of the cylinder or away from that side of the cylinder that is covered by the portion 23 of the cylinder head. Thus, the broken line 25 indicates the axis of the piston and the broken line 26 is drawn through the axis of the piston pin 24-. These broken lines clearly indicate the offset arrangement of the piston pin relative to the axis of the piston.

Figs 2, 3 and 1 diagrammatically illustrate the operation of the engine with the clearance therein considerably exaggerated to indicate the action of the piston. The arrow 2'? in Figs. 1, 2, 3 and 4; indicates the direction of rotation of the crank shaft. In Fig. 2 the piston is about half way up on its compression stroke and because of the angularit-y of the connecting rod the piston is pressed tightly against the right hand wall of the cylinder and all of the clearance is on the left hand side, that is the valve side of the cylinder. The piston is moving upwardly and parallel with the axis of the cylinder, and the mixture in the cylinder is being compressed in the cylinder and in the combustion chambe 21. The mixture that is between the portion 23 of the head and that half of the piston is beginning to eddy because of the approaching flat surfaces on the head and piston respectively, and this becomes more violent as the piston nears the top of its stroke as in Fig. 3. In fact, at this point the pressure on the piston under the head portion 23 is somewhat in excess of that over the remainder of the piston head and, due to this fact and the offset position of the piston pin 2%, the bottom of the piston is rocked across the cylinder somewhat as shown in Fig. 3. This causes no noise because the piston is movin upwardly and it does not move across bodily. The top of the piston has no chance to rock across to the opposite side of the cyliuder until about the time ignition takes place in the combustion chamber 21. This of course increases the pressure on the valve side of the piston and the piston will be rocked across to the position shown in Fig. 4', but tl is rocking action decreases the size of the space under the portion 23 of the head and the gases there form a cushion which helps to slow down the rocking action. This rocl ing will also carry with it the upper end of the connecting rod due to the fact that the rocking action must take place with the lower left hand corner of the piston as the axis of oscillation, and in this case also the piston does not bodily shiftacross from one side of the cylinder to the other. This rocking across is therefore like-wise quiet.

From the above it will be seen that the movement of the piston from one side of the cylinder to the other is by a two step process, that is, the lower end of the piston first moves across and then the upper end of the piston follows a little later. The piston then travels iii! All

downwardly from the position shown in Fig. i with the pressure all on the valve side of the cylinder.

As shown herein the piston is preferably made of aluminum so that the slight offset of the pin does not materially unbalance the weight of the piston at the upper end of the connecting rod. With this construction a great deal of latitude in manufacturing may I be allowed without producing a noisy engine.

While I have herein described in some detail a specific embodiment of my invention, which I deem to be new and advantageous and may specifically claim, I do not desire it to be understood that my invention is limited to the exact details of the construction, as it will be apparent that changes may be made therein without departing from the spirit or scope of my invention.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In an internal combustion engine, the combination of a cylinder, a piston therein, a connecting rod pivoted to the piston in slightly offsetrelation to the axis of the piston, and a cylinder head forming a combustion chamber and having a portion of the head on the side of the cylinder axis opposite the offset arranged to provide only slight clearance between said portion and the piston at the top of the compression stroke.

2. In an internal combustion engine, the combination of a cylinder, a piston therein, a connecting rod pivoted to the piston in slightly offset relation to the axis of the pis ton, and a cylinder head formed with a combustion chamber and with means for causing an excess of pressure against that side of the piston head opposite the offset, near the top of the piston stroke.

3. In an L-head internal combustion engine, the combination of a cylinder, a piston therein, a connecting rod pivoted to the piston in slightly offset relation to the axis of the piston and towards the valve side of the engine, and a cylinder head having a combustion chamber and having a portion of the head farthest removed from the valves arranged to provide only slight clearance between -said portion and the piston at the top of the compression stroke.

4. In an internal combustion engine, the combination with the cylinder, the piston therein, and the valve ports and valves arranged at one side of the cylinder, of a connecting rod pivoted to the piston at a point slightly ofiset from the axis of the piston and towards the valve side of the cylinder, and a head for the cylinder formed with a portion covering substantially that half of the cylinder farthest removed from the valve ports and so positioned that there is only slight clearance between the piston and that portion of the head at the top of the compression stroke, said head also having a re cess over the remainder of the cylinder and over the valve ports forming a combustion chamber.

5. In an internal combustion engine, the combination with the cylinder, the piston therein, the valve ports and valves arranged at one side of the cylinder, the crank shaft, and a connecting rod between the piston and crank shaft, a pivotal connection between the connecting rod and the piston slightly olfset from the axis of the piston and towards the valve side of the cylinder, and a head for the cylinder formed with a portion covering substantially that half of the cylinder farthest removed from the valves and so positioned that there is only slight clearance between the piston and that portion of the head at the top of the compression stroke, said head also having a recess over the remainder of the cylinder and over the valve ports forininga combustion chamber, said engine crank shaft rotating in a direction to bring the pressure, on the firing stroke, on the valve side of the cylinder.

6. In an internal combustion engine, the combination of a cylinder, an aluminum piston therein adapted for high speed operation, a connecting rod pivoted to the piston in slightly offset relation to the axis of the piston, and a cylinder head formed with a combustion chamber and with a portion arranged to provide only slight clearance for the top of the piston at the top of the compression stroke, said portion of the head being arranged on that side of the axis of the cylinder opposite the offset.

In testimony whereof I affix my signature.

JESSE G. VINCENT. 

